Growth response and fatty acid composition of rainbow trout (Oncorhynchus mykiss) fry fed diets containing different levels of soybean and egg lecithin

We investigated the effect of soybean and chicken egg lecithin on the growth performance, fatty acid profile and body composition of rainbow trout fry. Seven isonitrogenous and isolipidic diets were prepared by replacing 0, 2, 4 and 6 % soybean and egg lecithin instead of soybean oil in diets. Trout fry with initial average weight 120 ± 4.08 mg were randomly distributed in twenty-one 90-L tanks. Triplicate groups (165 fish per tank) of fry were fed to visual satiation at six meals per day for 40 days. Incorporation of 2 and 4 % egg lecithin led to increase in final weight, specific growth rate and weight gain compared with control group. Also, 4 % soybean lecithin had moderate effects on growth performance of fry. The fatty acid compositions of fry were influenced by dietary fatty acid. Fish fed egg lecithin showed higher amount of monounsaturated fatty acid than soybean lecithin and control groups. Fry fed soybean lecithin had significantly higher levels of polyunsaturated and n-6 fatty acid than egg lecithin and control groups. Soybean and egg lecithin induced higher amount of highly unsaturated fatty acid in lecithin groups compared with control group. The lipid and ash content of whole-body tissues were positively affected by percentages of soybean and egg lecithin in the diets. So 6 % soybean and egg lecithin induced higher amounts of lipid and ash body content. The results of our study indicated that dietary egg lecithin had growth-promoting effect, and rainbow trout fry had moderate lecithin requirement (at least 2 % as fed).     

Effects of stocking density and feeding levels on growth and feed efficiency of Nile tilapia (Oreochromis niloticus L.) fry

The effects of stocking density and feeding levels on larval survival, growth rates, feed utilization efficiency and body composition of Nile tilapia (Oreochromis niloticus L.) fry were investigated in two consecutive experiments. In experiment 1, swimup fry (0.016 g average body weight) were stocked in 20‐L fibreglass tanks, in a closed, recirculating indoor system, at five stocking densities (3, 5, 10, 15 and 20 fry L^?1) and fed a larval test diet (40% crude protein) to apparent satiation, three times a day, for 40 days. Fish survival, percentage weight gain and specific growth rate (% SGR) were negatively correlated with stocking density. The best performance was achieved at 3 fry L^?1. However, no significant differences in growth parameters were found between 3 and 5 fry L^?1. Body composition was not significantly affected by stocking density. In experiment 2, fry (0.016 g average body weight) were stocked at 5 fry L^?1, and fed a larval test diet (40% crude protein) at six feeding levels (10%, 20%, 25%, 30% and 35% BW day^?1) and to satiation, three times a day for 40 days. Fish growth rates and survival were extremely poor at 10% feeding level, and improved significantly with increasing feeding levels up to 30%, and levelled off with further increase in feeding levels. On the contrary, feed conversion ratio (FCR) and protein production value (PPV) were negatively correlated with feeding level. The lowest feeding level (10%) produced significantly lower body lipid and higher protein and ash than other feeding levels. The present results suggest that the optimum stocking density and feeding level of Nile tilapia fry are 5 fry L^?1 and 30% per day respectively.     

The Effect of Confinement in Hapas on Sex Reversal and Growth of Oreochronmis niloticus

Orechromis niloticus fry were effectively sex-reversed to males (>97%) when given a ration containing 60 mg methyltestosterone/kg for 28 days, independent of the length of time fry were confined to hapas (0, 7, 14, 28 days) before being released into outdoor 20-m² static water tanks. Fish from all treatments were raised an additional 30 days in the tanks and were fed a non-hormone treated feed. After 28 days of hormone treatment, fry stocked directly into the tank at 150/m² were the largest, with an average weight of 1.9 g. Those held in hapas for 28 days were significantly smaller (0.6 g) than those not held in hapas or held for a shorter period. After a total culture period of 58 days, mean individual weights and survival rates were similar among all treatments. The results of this study demonstrate that it is possible to sex reverse tilapia fry in open outdoor environments and reduce the steps in the nursery phase. Confinement in hapas is not necessary for successful sex reversal, and it limits growth.     

Effects of culture density and live prey on growth and survival of juvenile cuttlefish, Sepia officinalis

The effects of culture density on growth and survival of juvenile cuttlefish were tested. Groups of 1, 3 and 5 hatchlings were placed in small containers with bottom surface of 80 cm², obtaining individual densities of 125, 375 and 625 cuttlefish m^–2, respectively. Additionally, groups of 5 hatchlings were placed in containers with 2 different bottom areas (80 and 240 cm²), providing culture densities of 625 and 42 cuttlefish m^–2, respectively. A total of 120 hatchlings were used and experiments lasted for 40 days. No differences were found in growth between any of the densities tested throughout the experiment until 35 days old. After this, cuttlefish placed in isolation grew significantly larger. A second experiment was conducted in a flow through system, using two rectangular tanks with bottom surface of 0.5 m². Two groups of 25 cuttlefish hatchlings were used in this experiment, which lasted for 40 days. Both groups were fed live juvenile shrimp (Crangon crangon) during the first 5 days. Afterwards, one group was fed live fish fry of different species, while the other continued to be fed shrimp. After day 10 and until the end of the experiment, hatchlings fed shrimp grew significantly larger than those fed fish fry. Survival of hatchlings fed shrimp or fish fry after 40 days was of 100% and 68%, respectively. Total protein content of both prey types was similar. Therefore, the higher polar lipid content, especially due to the higher phosphatidylcholine and phosphatidylethanolamine levels observed in the shrimp, compared to fish fry could possibly be one of the major factor to explain the significantly higher growth rates for S. officinalis juveniles fed shrimp. Also, the percentage of polar lipids in the shrimp (47.4%) was closer to the one of juvenile cuttlefish (38.1%) than the composition of polar lipids in fish fry (10.4%). This could also be an important factor to explain the poor growth and survival obtained when feeding fish fry to the cuttlefish.     

Growth of control and androgen-treated Nile tilapia, Oreochromis niloticus (L.), during treatment, nursery and grow-out phases in tropical fish ponds

Abstract. Masculinization of sexually undifferentiated tilapia fry is achieved by oral administration of the androgen 17-α methyltestosterone (MT). An anabolic response to androgen treatment of tilapia has been reported. Growth of control and MT-treated tilapia was evaluated during consecutive treatment, nursery, and grow-out phases under conditions approximating commercial, semi-intensive tilapia farms in Central America. Oreochromis niloticus (L.) fry were fed a 0 or 60 mg/kg MT diet for 28 days. Growth curves for control and MT-treated fish did not have significantly different slopes. Mean harvest fry weights were similar, averaging 0·1 g/fry for both treatments. Fry were subsequently stocked into 0·2-ha nursery ponds for 94 days growth. Slopes of control and MT-treated fish growth curves were not significantly different. Mean final individual weights did not differ significantly between treatments. Control fish did not deviate significantly from the1:1 male: female ratio, but MT-treated fish were 97% males. Control male and MT-treated male fingerlings were stocked for grow-out into 0·1-ha organically fertilized earthen ponds. No significant difference in growth was observed between control and MT-treated fish. Mean gross yields after 150 days and mean final individual weights were similar for both treatments.     

Effects of Varying Concentrations of l-carnitine-incorporated Diets on Growth and Body Composition of Fry of Cirrhinus mrigala (Hamilton, 1822)

Experiment was conducted to ascertain the effect of l ‐carnitine on growth and body composition of Cirrhinus mrigala fry (0.342 ± 0.03 g) using five different concentrations (0.25, 0.50, 0.75, 1, and 0%) of l ‐carnitine‐incorporated diets for 120 d. At the end of trial, weight gain, feed conversion efficiency, and protein efficiency of fishes fed with 0.25% l ‐carnitine diet were observed to be significantly higher. Poor growth was recorded in the fry fed diet with no carnitine, while intermediate growth was observed when fed with 0.50, 0.75, and 1% l ‐carnitine‐incorporated diets. The analysis of body composition of C. mrigala fry indicated that there is no significant difference (P > 0.05) in moisture, protein, and ash contents, but significant difference (P < 0.05) was found in body lipid content of fry, fed with different concentrations of l ‐carnitine. Decrease in viscerosomatic and hepatosomatic indices were observed in fishes fed with l ‐carnitine‐incorporated diets. Results of this study indicated that diet containing 0.25% l ‐carnitine can promote higher growth in C. mrigala fry.     

Effects of Dietary Protein Levels on Gonad Maturation, Size and Age at First Maturity, Fecundity and Growth of Nile Tilapia

Six-week-old Nile tilapia (Oreochromis niloticus) fry with an average weight (SD) of 0.51(0.2) g were reared for 140 days on five formulated, isocaloric diets of different protein levels (25, 30, 40 and 45% by dry weight). Fish fed diets of higher protein levels (40 and 45%) showed better growth and feed conversion ratio than those on lower protein levels. Fast-growing fish matured earlier. Maturation rate was affected by the dietary protein levels. Males matured earlier than females: the first mature males were recorded when they were 14 weeks old, whereas the females matured after 18 weeks. In both sexes, mean percentage of mature fish rose with increasing dietary protein level, the percentage of mature males being higher than that of the females. Similarly, the percentage of mature fish rose with the increasing age of fish, with more than 50% males and females mature at the age of 22 and 24 weeks, respectively, the exception being the 25% protein diet fed fish, where the percentage of mature fish was below 50%. In all treatments, spawning was initiated when the fish were 22 weeks old. Smallest size at spawning of males and females was 9.2 cm (13.1 g) and 8.1 cm (8.9 g), respectively, and dietary protein levels influenced the size of fish at first maturity. For both sexes, no difference was found in the gonado-somatic index (GSI) among different treatments. Fecundity increased with increasing dietary protein levels, but significant differences were found only between 40–45% and 25–35% dietary protein levels. The relative fecundity (eggs g^–1 female) was higher at the lower dietary protein levels (25–35%) than at the higher dietary protein levels (40–45%). The dietary protein levels did not have any significant influence on the size and weight of mature eggs. The chemical composition of fish and mature ovaries was significantly influenced by the dietary protein level.     

Sex reversal and growth of Oreochromis spilurus (Günther) in brackish and sea water by feeding 17α-methyltestosterone

Abstract. An investigation was undertaken to study the effect of 17α-methyiteslosterone (17-MT) on the sex reversal and growth of tilapia, Oreochromis spilurus (Günther), in brackish water (3–5 ppt) and sea water (40 ppt). Seven experiments were performed; four in brackish water and three in sea water. Yolk-sac fry (1 or 3 day age) were immersed (7 or 24 h/day) in water containing hormone at a concentration of 0–10mg/l for 4–25 days. The swim-up fry were subsequently fed either normal or hormone-impregnated diets (30–70 mg/kg) for another 35 days starting from first feeding. The growth and SGR of fry were better in groups which received hormone both in water and food as compared with water or food alone. Immersion In 5–10 ppm (24 h/day) brackish water solution for 5 days did not bring any change in growth or sex ratio. However, immersion in sea water solution for 25 days (7 h/day) at a concentration of 1 ppm induced positive growth but no change in sex ratio. Higher doses either did not affect or reduced growth and SGR but induced higher percentages (77–83%) of males. Complete masculinization (100%) was observed only in brackish water when fish were immersed in 2·5 ppm solution for 4 days (24 h/day) and later fed 50 mg/kg in diets for 35 days. These results were further confirmed when the immersion schedule was modified to 10 days (7 h/day) and feeding 50–70 mg/kg hormone. It can be concluded from these studies that in brackish water complete masculinization of O. spilurus is possible through immersion in 5·0 ppm for a minimum of 75 h followed by feeding with 50 mg/kg food for a minimum of 40 days starting from first feeding.     

Effect of dietary phospholipid sources and levels on growth performance,enzymes activity,cholecystokinin and lipoprotein fractions of rainbow trout (Oncorhynchus mykiss) fry

This study was conducted to evaluate the effect of soybean lecithin (SBL) and chicken egg lecithin (EGL) on growth performance; pancreatic and intestine enzymes, cholecystokinin (CCK) and lipoprotein fractions of rainbow trout, Oncorhynchus mykiss (Walbaum) fry. Seven isonitrogenic and isolipidic diets were prepared by replacing 0 (as a control), 2%, 4% and 6% soybean and chicken egg lecithin instead of soybean oil in diets. Trout fry with initial average weight of 120 ± 4.08 mg, were randomly distributed in 21 90 L tanks. Triplicate groups (165 fish for each tank) of fry were fed each diet to visual satiation at six meals per day for 40 days. Dietary supplements of 2% and 4% chicken egg lecithin led to increase in fry final weight, weight gain and specific growth rate suggesting that moderate PL levels are needed during this stage of rainbow trout. Also 2% chicken egg lecithin caused significantly higher activity of amylase, lipase, phospholipase A₂, alkaline phosphatase (AP), aminopeptidase‐N (AN) and lower activity of leucine alanine peptidase (leu‐ala) in the digestive tract of fry than those in control group. Furthermore, fry fed 2% chicken egg lecithin had a higher ratio of AN/leu‐ala and AP/leu‐ala than that in the control group. Chicken egg lecithin increased significantly cholecystokinin (CCK) and chylomicron fractions of fry compared to control group. It is noteworthy that soybean lecithin had moderate effect on final growth, weight gain and specific growth rate of fry and induced significantly higher activity of amylase, lipase, phospholipase A₂ and secretion of CCK compared to control group. The results of this study indicate that dietary supplementation 2% chicken egg lecithin indirectly through some biochemical parameters improves growth performance of rainbow trout fry.     

Biotin in practical fish-meal based diet for Atlantic salmon Salmo salar L. fry

Groups of Atlantic salmon fry (0.19 g initial weight) were fed a fish-meal based starter diet with different supplements of biotin (0, 0.5, 1.0 and 1.5 mg biotin kg^–1) in triplicate tanks for 18 weeks. The basal diet contained 0.3 mg total biotin kg^–1. The experimental design included a negative control diet made by replacing 10% of the fish-meal with spray-dried raw hen's egg white.
Throughout the experimental period the fish grew to about 5 g and there were no significant differences in growth and mortality among the groups of fish fed the fish-meal diets. At the end of the experiment there were no significant differences in biotin level in the liver, while whole-body biotin concentrations correlated significantly with the dietary biotin concentrations. No significant increase in pyruvate carboxylase (PC) activity was found in livers from fish given different dietary levels of biotin. The control diet with egg white resulted in severe growth reduction and increased mortality compared with the other dietary groups. The concentrations of biotin in liver and whole body were decreased in fish fed egg white. Increased levels of glycogen and reduced PC activity in the liver were observed in this group after 18 weeks.
Histology of the gills showed no differences in appearance when fish were fed fish-meal based diets while the addition of egg white resulted in hypertrophy and hyperplasia of the gill tissue and extensive fusions of the secondary gill lamellae.
The results show that there is no need for supplemental biotin in practical fish-meal based diets for Atlantic salmon fry to achieve optimal growth, survival and maximal liver PC activity.     

Growth and fry production of Nile tilapia, Oreochromis niloticus (L.), on different feeding schedules

The effect of scheduled use of high‐protein and low‐protein diets on body weight and fry production of Nile tilapia, Oreochromis niloticus (L.), was determined. A preliminary feeding trial was first conducted on fingerlings. These were fed a high‐protein diet (H, 25% protein) or a low‐protein diet (L, 18% protein) daily, or diet H for 1–3 days followed by diet L for 1–4 days. Final body weight was significantly higher (P < 0.05) in fish fed diet H daily and in fish fed diet H for 2–3 days followed by diet L for 1 day (2H?1L and 3H?1L). Fingerlings on 1H?1L and 3H?2L had slightly lower growth. Based on the response of the fingerlings, five feeding schedules were tested with the broodstock. A high‐protein diet (HP, 40%) and a low‐protein diet (LP, 25%; same as H for fingerlings) were used. Feeding schedules significantly influenced body weight of female but not the male fish. Fry production was not significantly affected by the feeding schedule for broodstock. When growth, fry production and saving in feed cost were all considered, the broodstock on 1HP?1LP and 3HP?2LP feeding schedules both gave the highest overall performance. These findings give fish farmers an option in the management of feeding of tilapia broodstock.     

牛磺酸对鲤生长及血清T_3、T_4含量的影响

用牛磺酸作为饲料添加剂,以0.2%、0.4%、0.6%、0.8%的剂量将牛磺酸添加到基础饲料中,以基础饲料为对照,饲喂重(40.73±3.92)g的鲤60 d后,测定鱼体的相对增重率、饲料系数、血清中三碘甲状腺原氨酸(T3)及甲状腺素(T4)的含量,结果表明:牛磺酸显著地提高鲤的生长速度和血清甲状腺素的含量(P<0.05),极显著地提高鲤的血清三碘甲状腺原氨酸的含量(P<0.01),对饲料系数没有显著影响(P>0.05)。血清T3、T4含量的提高,是牛磺酸促进鱼体生长速度加快的重要原因之一。     

Interactive effects of dietary protein and live bakery yeast, Saccharomyces cerevisiae on growth performance of Nile tilapia, Oreochromis niloticus (L.) fry and their challenge against Aeromonas hydrophila infection

Yeasts used as a probiotic in fish diets could stimulate fish resistance against bacterial infection and could enhance the activities of digestive enzymes in fish guts. In addition to yeast importance, dietary protein is another important part in fish diets that should be carefully optimized to meet fish requirement. It is proposed that the yeast supplementation may enhance the dietary protein turnover and reduce the protein requirement for fish. Therefore, the interactive effects of dietary protein and yeast levels on the growth performance of Nile tilapia, Oreochromis niloticus (L.) fry and their challenge against Aeromonas hydrophila infection was evaluated. In the present study, ten experimental diets were formulated to contain either 35% or 45% crude protein (CP). For each protein level treatment, bakery yeast (Saccharomyces cerevisiae) was supplemented at 0.0, 0.50, 1.0, 2.0, or 5.0 g/kg diet. Fish (0.25–0.48 g) were distributed at a rate of 25 fish per 140-L aquarium. For each diet, triplicate aquaria were fed twice a day, 5 days a week for 12 weeks. Fish growth and feed utilization were significantly affected by either dietary protein or yeast levels alone, while no significant effect of their interaction was observed. The highest fish growth was obtained at 1.0–5.0 g yeast/kg diet at both protein levels; however, the fish performance at 45% CP was better than that fed on 35% CP diets. The optimum feed conversion ratio (FCR) was obtained when fish fed on 1.0–5.0 and 2.0–5.0 g yeast/kg diet at 35 and 45% CP, respectively. The cumulative fish mortality, after interperitoneal injection with A. hydrophila for 10 days, and bactericidal activity was significantly higher in fish fed 35% CP diets than those fed 45% CP diets. Both variables decreased significantly with the increase in yeast levels. The lowest bacterial count and bactericidal activity were obtained in fish fed 5.0 g yeast/kg diet irrespective to dietary protein levels. It could be concluded that the inclusion of live bakery yeast in practical diets could improve the growth performances, feed utilization, and physiological status of Nile tilapia fry and their challenge against A. hydrophila infection. Moreover, fish performance when fed 45% CP diet was better than those fed 35% CP diet. Based on these results, the most suitable yeast level for maximum Nile tilapia growth was determined to be 2.0 g yeast/kg diet with 45% CP diet; however, this level was recommended to stimulate their productive performance and enhances their resistance against A. hydrophila infection.     

Growth and survival of Atlantic salmon, Salmo salar L., fed different dietary levels of astaxanthin. First-feeding fry

Atlantic salmon fry hatched from pigment-free eggs and from eggs containing the pigment astaxanthin were fed eleven casein/gelatine-based purified diets with varying levels of astaxanthin, ranging from 0 to 317 mg kg^?1, to determine the optimum dietary astaxanthin level for satisfactory growth and survival during the start-feeding period. The fish were fed the experimental diets for a period of 11 weeks. No difference in performance was found between the two types of fry originating from the pigment-free eggs and those containing pigment. However, the dietary astaxanthin concentration was found to have a significant effect on both the growth and the survival of fry. Fish fed diets with astaxanthin concentrations below 5.3 mg kg^?1 were found to have marginal growth. In addition, mortality was high in the groups fed diets with astaxanthin concentrations below 1.0 mg kg^?1. The specific growth rate (SGR) was also affected by the dietary treatment. The lipid content was higher and the moisture content was lower in the fish fed the diets containing astaxanthin concentrations above 5.3 mg kg^?1. The vitamin A and astaxanthin concentrations in whole-body samples of the fry were significantly affected by the dietary level of astaxanthin. A plateau level in whole-body vitamin A concentration was observed at dietary levels of approximately 80 mg astaxanthin kg^?1 and higher, while no maximum astaxanthin concentration in whole-body samples was observed within the dietary levels used. The results suggest the need for a minimum dietary astaxanthin concentration of 5.1 mg kg^?1 to achieve maximum growth and survival during the start-feeding period. The results indicate a low bioavailability of vitamin A palmitate and acetate and the results also suggest a provitamin A function for astaxanthin during the same period.     

Effects of cellulase addition to canola meal in tilapia (Oreochromis niloticus L.) diets

The effects of commercial cellulase enzyme products on the nutritive value of canola meal (CM) were determined in tilapia fry. Nine diets were prepared by adding cellulase enzyme (1–5 g kg^?1) to control diet (containing no canola), low canola (41.7 g kg^?1 CM) and high canola (208.3 g kg^?1 CM). Tilapia fry was fed for 90 days, and growth, feed conversion ratio (FCR), body composition and nutrient digestibility were determined. Fish fed the diets containing the lowest levels of canola meal (41.7 g kg^?1) had similar final weight and FCR relative to the group fed the control diet, and high canola diet showed significantly lower growth than other groups (P < 0.05), irrespective of cellulase enzyme. The addition of canola meal to tilapia diets resulted in lower protein digestibility and cellulose digestibility. There were no significant differences in body compositions in all treatments. Addition of enzymes to canola meal diets had no significant effects on growth performance, body compositions and nutrient digestibility. The results of this study indicate that use in higher level of canola meal in tilapia diet was adversely affected growth parameters and FCR. Adding dietary cellulase enzyme in different rations to diets showed no significant differences in growth parameter.     

不同驯化方式对哲罗鱼仔、稚鱼生长和存活的影响

在水温8．9～14．2℃下,在平列糟（长3m,宽0．4m,高0．2m）中采用A、B和C组三种投喂方式驯养刚开口摄食、体质量0．129±0．07g的哲罗鱼（Huchotaimen）苗60d,以探讨驯化方式对哲罗鱼仔、稚鱼生长、存活和种群变异系数的影响：A组以浮游动物开口,投喂浮游动物3d,投喂水蚯蚓15d后,改投人工饲料;B组以水蚯蚓开121,投喂水蚯蚓15d后,改投人工饲料;C组直接以人工饲料开口。结果表明：C组体质量特定生长率（3．577±0．78％／d）,明显大于A组（3．132±0．87％／d）和B组（3．024±0．91）;A、B、C组的成活率分别为75．67％、74．87％和84．36％,C组明显大于A、B组;A、B和c组鱼体质量变异系数依次为21．47％、22．59％和11．32％,实验表明,直接以人工饲料开口是哲罗鱼规模化养殖中合理的驯化投喂模式。     

Effects of dietary sunflower oil on growth parameters,fatty acid profiles and expression of genes regulating growth and metabolism in the pejerrey (Odontesthes bonariensis) fry

Aquaculture fish diets usually contain an addition of fish oil to improve their nutritional value. The effect of the replacement of dietary fish oil (FO) by sunflower oil (SfO) on growth, fatty acid composition and expression of genes implicated in somatic growth, feed intake and fatty acid metabolism was studied in pejerrey fry. Fry were fed per 45 days with diets containing FO/SfO ratios of 100% FO; 50% FO:50% SfO; 20% FO:80% SfO; and 100% SfO. No differences were detected in growth and in the total per cent of saturated and monounsaturated fatty acids. Gh, ghr‐I and ghr‐II showed a higher mRNA expression in head and trunk of fry fed with 100% SfO diet. Expression of igf‐II was higher in trunk of fry fed with 100% SfO diet compared with 100% FO diet. The Δ6‐desaturase gene expression was upregulated in head and trunk of fry fed with 100% SfO diet. The nucb2/nesfatin‐1 gene expression decreased in the trunk of fry with increasing dietary SfO. We conclude that the replacement of fish oil by sunflower oil in pejerrey fry feed does not affect growth and is a viable strategy to reduce production costs of this fish.     

Food value of Brachionus plicatilis fed three selected algal species as live food for milkfish, Chanos chanos Forsskal, fry production

Abstract. The effects of three selected algal species, Tetraselmis tetrahele, Isochrysis galbana and marine Chlorella sp. on the population growth of Brachionus plicatilis was evaluated after 3, 5 and 7 days of culture. The rotifers fed on T. tetrahele showed superior growth with mean peak density of 92.5 individuals per ml to those fed on I. galbana (48.2 individuals per ml) and Chlorella sp. (47.2 individuals per ml) in 5 days. In another experiment, milkfish. Chanos chanos Forsskal, fry with initial mean body weight and standard length of 6.26 ± 1.07mg and 13.04 ± 1.40mm, respectively, were fed B. plicatilis reared on the three algal species for 30 days. Results showed that growth, measured in terms of gain in weight and length, was significantly different (P > 0.05) among treatments. Fastest growth was obtained in fry fed B. plicatilis cultured on T. tetrahele with mean gains in weight and length of 61.48 ± 8.40mg and 9.37 ± 1.68 mm, respectively, followed by fry fed B. plicatilis reared on I. galbana (43.56 ± 8.35mg and 6.25 ± 0.48mm). Milkfish fry fed B. plicatilis cultured on Chlorella sp. gave the poorest growth with mean gains in weight and length of 11.05 ± 1.82mg and 2.33 ± 0.29mm, respectively. Percentage survival ranged from 93.1 to 95.3 percent and was not significantly different between treatments (P < 0.05). The differences in population growth of B. plicatilis and consequently growth of milkfish fry was almost certainly attributed to the differences observed in the biological values of their algal diet, and in particular their protein and lipid contents. T. tetrahele and I. galbana improved the food value of B. plicatilis as live food for the milkfish fry. Their high dietary value was related to the higher algal protein and fat levels and contents of n-3 HUFA particularly 20:5n-3 and 22:6n-3 compared to B. plicatilis cultured on Chlorella sp. The results of the present study point to T. tetrahele as the most suitable food for the mass culture of the rotifer, B. plicatilis.     

Influence of dietary concentrations of protein,lipid and carbohydrate on growth,protein and energy utilization,body composition,and plasma titres of growth hormone and insulin-like growth factor-1 in non-transgenic and growth hormone transgenic coho salmon,Oncorhynchus kisutch (Walbaum)

This study compared the ability of juvenile non-transgenic (NT) and transgenic growth hormone (T; gene construct OnMTGH1) coho salmon (Oncorhynchus kisutch) to metabolically utilize energy from lipid and carbohydrate for growth at two dietary protein concentrations. Triplicate groups of size-matched (initial weight, 28.2–29.1 g) NT and T salmon held in 10.5–10.8 °C well water on a natural phototocycle (12.25 h → 8.25 h) were each fed one of four isoenergetic (~ 17.5 MJ of digestible energy (DE)/kg) dry diets twice daily to satiation for 83 days. These diets contained 340 g (LP) or 430 g (HP) of estimated digestible protein (DP)/kg and either 123 g (LL) or 164 g (HL) of estimated digestible lipid (DL)/kg at each DP level (dry weight basis). Estimated digestible carbohydrate (DCHO) concentrations ranged from 45 to 269 g/kg to equalize dietary DE. Under the preceding conditions 46–66% of NT and 18.7–27.5% of T coho, depending upon diet treatment, exhibited no growth or lost weight during the study. NT coho are known to grow slowly or lose weight between the fall equinox and winter solstice but this was unexpected for T coho. Considering all fish T coho, regardless of diet treatment, exhibited significantly higher specific growth rates (SGR) than NT fish due to enhanced feed intake, feed and protein (gross and available deposited) utilization and generally improved available energy utilization. Diet treatment did not affect the growth performance of T fish. Within NT fish, the HP diets supported best gross and available protein and energy utilization. SGR values for growing fish (F_G) only followed identical trends to those for all fish in relation to diet treatment. Regardless of fish genotype, terminal hepatosomatic indices for F_G were directly related to dietary DCHO content and maximum values were noted in NT fish fed LP–LL (significantly higher than observed in NT or T fish fed HP–HL). Final whole body protein concentrations adjusted for dissimilar fish size were higher in T fish fed HP–HL than in T fish fed LP diets and NT fish fed LP–LL. This was also true for T fish fed HP–LL versus T fish fed the LP diets. Within HP groups, whole body lipid and energy contents were generally higher in NT versus T fish whereas within the LP groups energy content was significantly higher in T versus NT fish and was highest in T fish fed LP–LL. Terminal plasma titres for GH and IGF–1 (all fish) were significantly higher in T than in NT fish and were generally uninfluenced by diet treatment. Non-growing NT and T fish had elevated GH relative to NT and T fish that grew. Also, GH was higher in growing T fish relative to growing NT fish whereas the opposite was true in non-growing fish. Plasma IGF-1 levels were higher in growing NT and T fish than in their respective non-growing counterparts. Within F_G only, IGF-1 levels were higher in T versus NT fish.It is concluded that T coho have enhanced ability to effectively utilize DE from DCHO relative to NT fish especially when DP is near the bottom of the optimal range and DL is concurrently suboptimal for NT fish. This is likely due to the elevated titres of GH, IGF-1 and 3,5,3′-triiodo-l-thyronine (measured in another study) in T fish. Also, the enhanced ability of T fish to store energy under these dietary conditions suggests enzymatic improvements in their anaerobic and aerobic metabolism of glucose.     

Evaluation of Decapsulated Artemia Cysts in Hatchery Diets for Channel Catfish Ictalurus punctatus Fry and Effects on Subsequent Fingerling Production

Abstract.— Two 10-d hatchery growth trials were conducted to determine if differences in growth, body composition, and survival existed among catfish fry Ictalurus punctatus fed a diet of 100% catfish-starter (CS) or CS in combination with decapsulated Artemia cysts (DAC) at 25%, 50 % , or 75% of diet weight. A 120–d production trial was undertaken immediately following the first hatchery trial to evaluate the effects of diet on production characteristics (survival, length, weight, feed conversion ratio, and total yield) of fingerling catfish produced from hatchery-raised fry. Fry fed diets containing DAC weighed 61–98% more ( P < 0.05) than fry fed only CS. The size differential of DAC-fed fry was maintained through 120 d of growth in simulated nursery ponds (0.001-ha earthen-bottom pools). The increased growth of fry fed DAC might have been related to differences in dietary lipid content, amino acid composition, or digestibility of CS and DAC. Body weights of fingerlings produced under simulated production conditions from fry fed hatchery diets containing 50% and 75% DAC were 17% and 25% higher, respectively, 130 d post-hatch, than fingerlings produced from fry fed only CS. In addition, the total yield of fingerlings produced from fry fed 75% DAC was 17% greater that that of fingerlings produced from fry fed only CS. The increased performance of fingerlings produced from DAC-fed fry could have resulted from their larger size at stocking, since larger fry might be capable of capturing natural food organisms and ingesting prepared diets more effectively than smaller fish. CS-DAC diet combinations could be used to increase weight gain of hatchery-raised fry if the cost-benefit ratio of adding DAC to the standard hatchery diet warrants its use.